ADS4129: Can't detect output clock

joao presa

Part Number: ADS4129

Hi,

I can't detect any output clock. I'm using an lvpecl input. The P of this clock signal side can be seen on the follwing image (which follows the 1.6vpp differential):

-The output clock is just two DC values 0.9V and 1.2V.

-The VCM is ok.

-At the moment I don't have and input signal connected and I'm lacking the closest decoupling capacitors.

-I also tried it at higher frequencies (15MHZ,125MHz).

-I didn't use the spi interface yet.

Am I doing something wrong or did I kill de ADS4129?

Thank you,

Best Regards,

Joao

over 3 years ago

0 RJ Hopper over 3 years ago

TI__Mastermind 18065 points

I am not following. I assume the picture is the input clock and you cannot detect the output clock. You may indeed need to use the SPI to initialize the part properly.

--RJH

0 joao presa over 3 years ago in reply to RJ Hopper

Prodigy 170 points

Yes, the picture is the input clock. I can’t find anything in the datasheet that would require the spi interface to enable the output clock. I have the output enable pin and dfs correctly connected.

0 joao presa over 3 years ago

Prodigy 170 points

I tried using the SPI interface but it's also not working. I double checked all the voltages (DRVDD,AVDD,GND,VCM,pullups/down) and they are ok. The DC voltages from the lvds interface are also present. I also probed the SPI signals to make sure they are accordingly with the datasheet.

Could I, somehow, have damaged the digital part of the chip? Or it's unlikely and I'm just missing something?

0 David Chaparro over 3 years ago in reply to joao presa

TI__Genius 11960 points

Joao,

I tested one of our EVM's and I am able to see the output clock right after powering the board. So I am not sure what your issue could be.

Are you checking directly on the clock output pin of the ADC?

Regards,

David Chaparro

0 joao presa over 3 years ago in reply to David Chaparro

Prodigy 170 points

Thank you, David Yes, I have tested in the pin of the ADC. Joao

0 David Chaparro over 3 years ago in reply to joao presa

TI__Genius 11960 points

Joao,

Would it be possible to see the schematic for the clock input and output? This would allow us to see if anything else could be causing the issue.

Also, have you checked to make sure you are providing the ADC with the correct power, AVDD and DVDD.

Regards,

David Chaparro

0 joao presa over 3 years ago in reply to David Chaparro

Prodigy 170 points

Thank you, David

I managed to solve the problem. I replaced the IC and this time didn't leave the analog input floating. It seems to work now.

If you want I can still share the the schematic for the clock.

Regards,

Joao

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ADS4129: Can't detect output clock